My brother and I started playing APBA baseball in the early '60s. Wore out more than one cards and accessories (in fact, I've still got a huge box full of seasons from around 1965 into the mid '70s - since I'm on a fixed income and don't have time to play I'm thinking of selling them).
Enough of that except to say, playing one season against another altered player stats. Having players in the '70s hit against the pitchers before '69 did alter their ability. And even some of the hitters had the same problems.
Next, and to get to the point, I've used several players, in OL leagues, time and time again, and their stats seem to change, some times drastically, each each time they're drafted. Sometimes I get the idea that, when you draft, you don't actually know which year the player you drafted you'll end up with. For instance, sometimes Ozzie Smith is unbelievable, and sometimes not that great. Sometimes you can't get Stan the Man out and sometimes he's not that great.
I kind of believe that, when you draft, Whatif kind of flips a coin to seen which season you end up with.
Now, after all that, a question. Do I have to draft players from 1901 - or close to that - to start? Or, could I, in the first season, draft - say Johnny Bench in his rookie year and play him until he retires?